Email masking policy (predefined)

The predefined Email policy masks a selected column by generating a new email address for each input value.

The Email policy generates a replacement email address for each input value. You can control whether the output is deterministic or randomized, preserve or modify the local part (before @) and domain (after @), apply a separator, set the output case, supply a custom domain list, or replace the local part with a prefixed identifier.

An email address consists of two parts separated by @: the local part (the name segment before @) and the domain (the segment after @). The policy generates a replacement local part and domain independently, subject to the configured options.

Note: Custom domain values do not include the leading @ (for example, ibm.com). The @ is added automatically between the local part and the custom domain in the output.

Configuration options

Use the following options to configure the Email policy.

Masking Method (required)

Controls whether the same input always produces the same output.

Repeatable — the same input value always produces the same output.
Random — each transformation produces a different output, even for identical inputs.

Email case (required)

Controls the case of the entire output email address.

Table 1. Email Case options
Option	Behavior
Normal	Output uses generated or preserved casing.
Upper	Entire output is uppercase.
Lower	Entire output is lowercase.

Preserve Email Name (optional)

Preserves the original local part verbatim in the output, including its original separators and casing. The domain is still generated or replaced according to other settings. Incompatible with User Prefix and Use First Character Only.

Use First Character Only (optional)

Reduces the local part to its first character followed by the remainder after the first separator. Works with all separator types (., -, _). For example:

john.doe → j.doe
TRYING-othername → T-othername
test_RANDOMname → t_RANDOMname

Incompatible with User Prefix and Preserve Email Name.

Preserve Domain Name (optional)

Preserves the original domain of each input row verbatim in the output. The local part is still generated or modified according to other settings.

Email Separator (optional)

Character or characters to use as the separator in the output local part. Replaces any existing separators in the generated or preserved local part. Incompatible with User Prefix.

Custom Domains (optional)

A comma-separated list of domain values to use in place of a generated domain (for example, ibm.com,example.com). Domains are assigned randomly across rows.

User Prefix (optional)

A literal string prepended to randomly generated digits to form the entire local part (for example, employee → employee1423). Replaces any generated or preserved local part. Incompatible with Preserve Email Name, Use First Character Only, and Email Separator.

The following options are mutually incompatible:

Table 2. Email policy option incompatibilities
Option	Incompatible with
User Prefix	Preserve Email Name, Use First Character Only, Email Separator
Use First Character Only	User Prefix, Preserve Email Name

API configuration (policy_metadata)

Use the following keys to configure the Email policy through the API.

Table 3. Email policy_metadata fields
Key	UI field	Type	Description
`algo`	Masking Method	String	`"repeatable"` (default) `"random"`
`case`	Email Case	String	`"normal"` `"upper"` `"lower"` Or use `""` for default (normal)
`customDomains`	Custom Domains	String	Comma-separated list of domains (for example, `"ibm.com,example.com"`). Use `""` for none.
`firstChar`	First Character Only	Boolean string	`"true"` to use first character only `"false"` to keep all characters
`keepDomain`	Preserve Domain Name	Boolean string	`"true"` to preserve the original domain `"false"` or `""` to generate
`keepName`	Preserve Email Name	Boolean string	`"true"` to preserve the original local part `"false"` or `""` to generate
`separator`	Email Separator	String	Separator character or characters to use in the output local part. Use `""` for none.
`userPrefix`	User Prefix	String	Literal prefix string. Use `""` for none.

{
  "algo": "repeatable",
  "case": "normal",
  "customDomains": "ibm.com",
  "firstChar": "true",
  "keepDomain": "false",
  "keepName": "false",
  "separator": "",
  "userPrefix": ""
}

Known limitations

The Email policy has the following limitations.

Use First Character Only reduces to the first character regardless of separator type: The reduction applies to all separator types. The first segment of the local part is reduced to its first character; everything after the first separator is preserved. For example, TRYING-othername → T-othername.
If you do not have custom domains and set keepDomain to false, the domain output can be unexpected: To avoid this issue, set keepDomain to true unless you have custom domains configured.
User Prefix numeric suffixes are not guaranteed to be unique across rows: The numeric suffix appended to a User Prefix is randomly generated and may coincidentally repeat across rows or runs under the Random algorithm.
Incompatible option combinations produce unexpected output without a warning: Configuring incompatible options (for example, User Prefix with Preserve Email Name) may produce unexpected results. Refer to the option compatibility table before combining options.